CARBON AND NITROGEN MINERALIZATION OF HARVESTING RESIDUES OF PINUS-SYLVESTRIS L DURING AEROBIC LABORATORY INCUBATION

The carbon and nitrogen mineralization dynamics of Pinus sylvestris L. harvesting residues, when mixed with an acidic, nitrifying fen peat, were studied during aerobic, laboratory incubation at 20-degrees-C ove r 12 weeks. Green needle, brown needle and fine root showed a pattern of curvilinear decline in C mineralization rate with time. The total a mounts of C mineralized from those residues, expressed as a percentage of their initial C content, were 52, 41 and 16%. Stem bark and stem w ood mineralized more slowly; the value for stem bark was near zero. Wi th the exception of stem bark, the harvesting residues enhanced the mi neralization of added C-14-labelled glucose. During the early decompos ition of the pine residues, the degree of net N immobilization of mine ral N was related to the initial C/N ratio or total N concentration of the residues and net N mineralization was negatively correlated with mineralization of C. The remineralization rate of freshly immobilized N was estimated as seven times faster than the mineralization rate of the more recalcitrant native N from the fen peat. The added pine resid ues did not influence measurably the nitrification capacity of the fen peat.